Fix crash when changing navigation modes

- The controller is only set on the active button, and when we tear
  down the nav bar, we try to update the controller from the other
  button

Bug: 132201048
Test: Switch navigation mode, ensure no crash
Change-Id: Id324c67946769193a4decab1a3d5e9d3967fc6fb

packages/SystemUI/src/com/android/systemui/statusbar/phone/RotationContextButton.java

@@ -66,7 +66,9 @@ public class RotationContextButton extends ContextualButton implements
 
     @Override
     public void onDestroy() {
-        mRotationButtonController.cleanUp();
+        if (mRotationButtonController != null) {
+            mRotationButtonController.cleanUp();
+        }
     }
 
     @Override